1. Field of the Invention
The present invention relates to on-board mounting electronic apparatus mounted to circuit boards of end users and also to an on-board mounting electric power supply such as, for example, a DC/DC converter or the like.
2. Description of the Prior Art
Typically, for this kind of on-board mounting electronic apparatus, represented by an electric power supply provided with, for example, a DC/DC converter or the like, an electric power supply 57 serving as such on-board mounting electronic apparatus is shown in FIG. 3, for example, which comprises: a metallic board 51 formed by printing conductive patterns on one surface, i.e., an underside surface of a plate-like board member made from aluminum or the like with an insulation layer provided therebetween; a plurality of conductive terminal pins 52 for connection with external, extending from an underside of the metallic plate 51; an additional board 55 disposed opposite to the underside of the metallic board 51 and connected electrically to the metallic board 51 via the terminal pins 52 and other connector pins 53, said additional board 55 having a variety of electronic components 54 mounted on one or both surfaces thereof which generate comparatively small amount of heat; and a case 56 provided under the metallic board 51 in a manner that covers the board 55.
By inserting tip ends of the terminal pins 52 protruding from the underside of the case 56, into plated through-holes of circuit boards prepared by users in advance and then by fixing them by means of soldering, a thin and flat shaped electric power supply 57 and the circuit boards (not shown) are electrically connected to one another with the former being opposite to the latter.
In such electric power supply 57 assembled by using the above-mentioned metallic board 51, heat generating components 58 such as a main switching element, a rectifier diode and the like are mounted on the underside of the metallic board 51. Therefore, a heat sink 59 is attached to an upper side of the metallic board 51 so as to dissipate heat from the heat generating components 58. However, as the heat generating components 58 have to be mounted only on one side of the metallic board 51, there occurs a problem that the above-mentioned additional board 55 for mounting electronic components 54 thereon, must be provided, in addition to the metallic board 51.
To eliminate such problem, there is proposed an electric power supply 71 shown in FIG. 4 as another type of such an on-board mounting electronic apparatus. The electric power supply 71 comprises an apparatus body 75 with an electric power source circuitry, said electric power source circuitry including a board 73 having heat generating components 72 mounted on one or both sides thereof and a plurality of conductive terminal pins 74 for connection with the external, extending from an underside of the board 73. Thus, the apparatus body 75 is placed in a box-like case 76 whose interior is filled up with heat conductive resin 77 so that heat from the heat generating components 72 is transferred from the heat conductive resin 77 to the case 76 to dissipate heat outward. Depending on cases, a heat sink (not shown) is mounted on a flat upper surface of the case 76 to dissipate heat therefrom. According to such electric power supply 71, a variety of components including the heat generating components 72 can be mounted on both surfaces of the board 73 so that all of components can be mounted on a single sheet of the board 73.
According to the electric power supply 71 shown in FIG. 4, however, the apparatus body 75 has to be placed in the case 76 and then filled up with heat conductive resin 77 in order to enhance a heat dissipating performance of the apparatus body 75. As a result, it is difficult to enhance the heat dissipation performance of the apparatus body 75, in a simple manner.
To eliminate the abovementioned problem, it is, therefore, an object of the present invention to provide an on-board mounting electronic apparatus and an on-board mounting electric power supply which enable the enhancement of heat dissipation performance thereof with a simple structure despite electronic components being mounted on a common and single board.
An on-board mounting electronic apparatus according to a first aspect of the present invention includes an apparatus body composed of a main board and terminals for connecting the main board with an external circuit board, said terminals extending from an underside of the main board, wherein there is provided a heat dissipation plate which is thermally connected with upper surface of heat generating components mounted on the abovementioned main board
Thus, in an apparatus body operating alone, only thermally connecting the heat dissipation plate with the upper surface of the heat generating components mounted on the main board allows heat from the heat generating components to be transferred directly to the heat dissipation plate mounted on the main board, thereby effectively dissipating heat therefrom. Accordingly, the heat dissipation performance of an apparatus body can be enhanced with a simple structure despite structural components being mounted on a common and single board.
The abovementioned also applies to an on-board mounting electric power supply according to another aspect of the present invention, wherein the dissipation performance of an apparatus body can be enhanced with the simple structure in the same way. Specifically, in this case, the enhanced heat dissipation performance enables the electric power supply to output greater power.
An on-board mounting electronic apparatus according to a second aspect of the present invention is one where stud members provided in the abovementioned heat dissipation plate is fixed on the circuit board in addition to the structure of the first aspect of the present invention.
In this case, the heat dissipation plate is arranged in a steady state at a predetermined height by fixing the stud members on the circuit board. As a mounting height relative to the circuit board can be simply adjusted by using the stud members, the mounting height from the circuit board to the upper surface of the heat dissipation plate can be simply adjusted to a desired value when an electric apparatus is connected to the circuit board by using terminals.
The abovementioned also applies to an on-board mounting electric power supply according to another aspect of the present invention, wherein a mounting height from the circuit board to the upper surface of the heat dissipation plate can be simply adjusted to a desired value.
An on-board mounting electronic apparatus according to a third aspect of the present invention is one where tap holes for fixing a heat sink arranged on the upper surface of the heat dissipation plate are formed in the stud members in addition to the first aspect of the present invention.
In this case, the stud members can be used not only for arranging the heat dissipation plate at a predetermined height but also for fixedly attaching the heat sink arranged on the upper surface of the heat dissipation plate.
The abovementioned also applies to an on-board mounting electric power supply according to another aspect of the present invention, the stud members can be used also for fixedly attaching the heat sink arranged on the upper side of the heat dissipation plate.
In a preferred form of the invention, the aforementioned terminals may comprise at least a pair of input terminals and at least a pair of output terminals.
Thus, an input voltage from the input terminals can be transformed to a desired voltage to output from the output terminals.
In a further preferred form of the invention, the main board may have a rectangular shape and the aforementioned input terminals and output terminals may be respectively arranged along both shortish sides thereof.
In this case, the input terminals and the output terminals can be respectively arranged in good order along both shortish sides of the rectangular-shaped main board.
In a still further preferred form of the invention, the main board is one wherein both shortish sides thereof have a length of 36.8 mm while both longish sides thereof 57.9 mm.
This enables the provision of an electric power supply with a dimensional standard that meets the needs from the market.